Manufacture of multi-wall bag having heat-sealed liner



c. E. DAVIS 3,097,618 MANUFACTURE OF MULTI-WALL BAG HAVING HEAT-SEALED LINER July 16, 1963 3 Sheets-Sheet 1 Filed D60. 1, 1960 H MMMMMUWW M HW MW INVENTOR. CRAIG E. DAV/s,

July 16, 1963 'c. E. DAVIS I MANUFACTURE OF MULTI-WALL BAG HAVING HEAT-SEALED LINER 3 Sheets-Sheet 2 Filed Dec. 1, 1960 INVENTOR. 012A 16. E. DAV/5,

July 16, 1963 c. E. DAVIS 3,0

MANUFACTURE OF MULTI-WALL BAG HAVING HEAT-SEALED LINER Filed Dec. 1, 1960 5 Sheets-Sheet 3 INVENTOR. CRAIG E. DAws,

ATTO R N EYS United States Patent Ohio Filed Dec. 1, 1960, Ser. No. 73,050 4 Claims. (Cl. 112-10) This invention relates to multi-wall bags and more specifically to a stitched end bag having a heat-sealed inner ply or liner formed as an integral part thereof, and to apparatus and procedures for producing such bag structure in a high speed continuous operation.

Conventional stitched end m-ulti-wall bags are formed by concurrently tubing a plurality of webs of bag forming material, such as kraft paper, about a former and thereafter severing the tubes into bag lengths which are then fed crosswise to a stitching machine where one or both end edges of the bag lengths are wrapped with tape which is stitched to the bag end to thereby provide a tight closure. Such bags may. be formed with or without gussets along their opposite side edges and if both ends of the bag are taped and sealed, one corner of the bag is provided with a valve and sleeve structure by means of which the bag may be readily filled and sealed.

In recent years there has been an increased demand for proofed bags, i.e. bags which will protect their contents against moisture and vapor, and while it has hitherto been proposed to form one or more of the bag plies from a laminated material, such as a layer of bitumen sandwiched between plies of paper, such bag structures are difiicult to close, particularly where the ends of the bag are stitched, since the bitumen fouls the stitching needles and, in addition, a proofed seal is not effected across the ends of the proofed ply or plies. Accordingly, where a proofed multi-wall bag is required, the industry has adopted the practice of inserting a pre-formed liner in the multi-wall bag subsequent to its formation. The insertion of the liner is essentially a hand operation; and while mandrels have been provided for supporting the liners during insertion, the operation nonetheless requires individual handling of the bags and materially increases the cost of the lined bags. Such lined bags are also subject to certain difiiculties both in filling and in use. The liners are usually formed from non-fibrous films, such as polyethylene, and hence are limp and, being unattached to the bag proper, are difiicult to maintain open for filling. Once filled, it is currently the custom to simply tie the mouth of the liner in a knot to close it, whereupon the open end of the bag is closed in conventional manner, as by tape and stitching. In the hands of the user, such lined bags also present difficulties in that, for the most part, they are used to package powdered or granular material used in batch lots which, for example, may be dumped in a beater or vat. The customary practice is to simply slit the bag across one end, whereupon it is inverted and the entire contents dumped in the beater or vat. Since the liners are unattached, they readily slip from the cut bag with the result that the beater or vat may be contaminated or fouled by the unwanted liners.

Accordingly, a principal object of the instant invention is the provision of a m-ulti-wall bag provided with a heatsealable inner liner which is inserted as an integral part of the bag making operation and which is permanently affixed to the bag, being stitched to the paper plies as their ends are closed.

A further object of the instant invention is the provision of apparatus by means of which continuous webs of bag forming material, including a tubular web of heat scalable liner material, such as polyethylene, are continuously formed into bag tubes, severed into individual bag lengths, whereupon the bag lengths are subjected to a heat sealing operation as an incident of their tape and stitching, so that the resultant liner is heat-sealed and hence proofed at its sealed end or ends.

Still a further object of the instant invention is the provision of procedures whereby bags of the character just described may be manufactured in an essentially continuous high speed production line operation.

The foregoing, together with other objects of the instant invention which will appear hereinafter or which will be apparent to the skilled worker in the art upon reading these specifications, are accomplished by that construction and arrangement of parts and by that apparatus and procedures of which an exemplary embodiment shall now be described.

Reference is now made to the accompanying drawings wherein:

FIGURE 1 is a schematic side elevational view of mechanism for forming webs of material into tubular bag lengths with the innermost ply comprising a tube composed of non-fibrous film.

FIGURE 2 is a plan view of a stitching machine in accordance with the invention wherein the bag lengths are taped, stitched and heat sealed across their stitched ends, all in a continuous operation.

FIGURE 3 is a vertical sectional view taken along the line 3-3 of FIGURE 2.

FIGURE 4 is a fragmentary plan view with par-ts broken away of the corner of a bag formed in accordance with the instant invention.

FIGURE 5 is an enlarge-d fragmentary perspective View showing details of the heat sealing bars and their mode of operation.

FIGURE 6 is an enlarged fragmentary side elevational view of the sealing bars illustrating the pantograph linkage controlling movement of the heating bars.

FIGURE 7 is a fragmentary plan view similar to FIG- URE 2 but showing an alternative arrangement wherein the bag lengths are heat sealed prior to taping and stitching.

Referring first to FIGURE 1 of the drawings, there is illustrated a conventional bag tubing device wherein webs of bag forming materials 1, 2, 3 and 4 are provided in rolls 1a, 2a, 3a and 4a, it being understood that suitable roll stands will be provided to permit the rolls to be unwound and the webs advanced for tubing.

In accordance with the instant invention, a tubular liner 5 is fed from a roll 5a so as to lie innermost when the webs are tubed. It will be understood, of course, that the number of Webs employed does not constitute a limitation on the invention and will be governed by the strength requirements of the bags being formed. Since the tubular liner 5 is preformed, preferably comprising seamless polyethylene tubing, it will be of a width substantially less than the width of the paper Webs and will be aligned relative thereto so that the webs will be folded about the liner and tubed in the conventional offset relation. In a typical bag construction, the Webs 1 through 4 will comprise 41" wide kraft paper, whereas the polyethylene tubing will be 19 /2" wide.

As the Webs and liner advance they are contacted by the usual dancing rolls 6, web guides 7, and cross p asters 8, the cross pasters serving to apply stripes of adhesive to the paper webs only, the liner being preferably passed around a guide roll 9 and juxtaposed to the innermost web 4 subsequent to its passage beyond the cross paster. The cross paster acting upon the innermost web 4 may also be utilized to apply appropriate adhesive areas for securing the liner to the innermost paper ply adjacent what will become the mouths of the bag lengths.

The paper webs are tubed by means of a conventional former or mandrel beneath which the webs and liner are fed, the liner underlying the mandrel so that the opposite side edges of the webs will be folded thereabout and seamed, suitable combining rolls 11 serving to advance the tubed webs and press the juxtaposed marginal edges of the webs into tight adhesive engagement. Thereafter, the tubular structure is severed into individual bag lengths by means of the cutofi knife 12 operating in timed relation to the speed of travel of the webs.

From .the tuber just described, the bag lengths are fed [to a second machine section which, as seen in FIG- URE 2, comprise a supporting frame 13 mounting conveyor chains =14 upon which the bag lengths 15 are deposited and advanced in spaced apart relation by means of trailing dogs 16. Any suitable conveyor and feeding mechanism may be employed -to deposit the bag lengths 15 on the conveyor chains 14, and such equipment does not constitute a limitation upon the instant invention.

As the bag lengths 15 are advanced by the conveyor chains, they are held in place by suitable hold down means 17 which assist in advancing the bag in proper alignment for taping and stitching. In the embodiment illustrated, only the bottom ends of the bag lengths are taped and stitched, the tape 18 being fed from a supply roll (not shown), around a vertically disposed guide roll 19 and through sweeps 20 which act to fold the tape about the end edge of the bag lengths. A continuous line of stitching is then applied by means of the stitching machine 21, as will be readily understood by the worker in the art.

Upon passage beyond the stitching device, the bag lengths enter a heat sealing section of the machine wherein the heat sealer 22 acts to seal together the lowermost ends of the tubular liners on both sides of the line of stitching passing therethrough. Prior to being contacted by the heat sealer, the bag sections are subjected to the action of a set of leading pinch rolls 23 which are driven in timed relation to the trailing pinch rolls 24 lying beyond the heat sealer, with the trailing pinch rolls 24 driven at a slightly increased speed so that the stitched ends of the bag lengths lying therebeween will be placed under tension. In this connection, it will be remembered that the bag lengths are joined together by a continuous length of tape and stitching which, upon being drawn taut, effectively flattens the bag plies for contact by the heat sealer. 1

As will be seen in FIGURES 5 and 6, the heat sealer preferably comprises an upper heating bar 25 and a lower heating bar 26 joined together at their opposite ends by pantograph linkages 27 by means of which the heating bars may be juxtaposed to opposite sides of the bag lengths when the machine is in operation and retracted to an inoperative position when the machine is stopped. To this end, the heat sealer includes a mounting frame 28 which, as seen in FIGURE 5, may be in the form of an angle bar the vertical flange of which mounts bearings 29 which rotatably receive the stub shafts 30 fo1ming a part of the linkage members 27. Movement of the heating bars to and from bag contacting position may be conveniently controlled by pneumatic cylinder 31 which may be secured to mounting frame 28 by means of bracket 32, the cylinder having a piston rod 33 the 'free end of which terminates in a yoke 34 to which an arm 35 is pivotally attached, the arm being fixedly secured to the stub shaft 30 of one of the pantograph linkages. Thus, when the piston rod 33 is extended, the pantograph linkages and the heating bars will be moved in one direction, and when the piston rod is retracted, the heating bars will be moved in the opposite direction, thereby moving them to and from their operative position.

The opposite ends of the pneumatic cylinder 31 are connected through conduits 36 and 37 (FIGURE 3) to solenoid controlled valves 38 and 39 arranged to be opened and closed in synchronism with the starting and stopping of the machine drive. The solenoid valves may be conveniently coupled to the starting and stopping circuits for the drive motor, the valves acting to alternately pressurize and vent the opposite ends of the cylinder. Preferably, a pressure regulator 40 will be provided -to regulate the pressure of the compressed air utilized to move the heating bars to the operative or sealing position, thereby providing for the application of controlled pressure to the heating bars.

As will be seen from FIGURE 5, each of the bars is provided with a centrally disposed longitudinally extending channel or recess 41 adapted to overlie the line of stitching which otherwise interrupts the essentially planar ends of the bags and assures positive contact of the inner surfaces of the heating bars with the bag walls. Thus, and as will be seen in FIGURE 4, two distinct seam lines will be formed across the end of the tubular liner 5, the outermost seam line 42 lying beyond the line of stitching 43, and the innermost seam line 44 lying to the inside of the line of stitching. Such arrangement assures a positive seal of the liner and, as will be evident, it is securely stitched in place as an integral part of the bag end.

Referring again to FIGURE 5, the heating bars are each preferably formed in two parts, designated 45 and 46, having a mating central opening 47 in which a heating element may be conveniently placed, the parts 45 and 46 being bolted or otherwise secured and covered with asbestos 48, the asbestos insulating the sides and tops of the bars.

While a single heating element may be employed for each of the heating bars 25 and 26, it is preferred that a plurality of such elements be employed, each extending throughout a portion only of the bars. Such arrangement permits controlled heating of the bar; and, as will be evident from FIGURE 2, a series of individual thermostatic controls 49 may be provided to control the amount of heat generated by the heating bars. This is particularly desirable since the amount of heat required will vary depending upon the number of plies making up the bag walls and the caliper of the paper employed. With the arrangement just described both the heat and pressure of the sealing bars can be readily adjusted to suit the conditions of use.

Upon passage beyond the heat sealer, the bag ends are preferably contacted by pressure rolls 50 which apply pressure to the seam area. Upon passage of the bag lengths beyond the trailing pinch rolls 24, the tape and stitching is subjected to the cutter 51 which acts to sever the tape and stitching intermediate adjacent bag lengths, thereby freeing the bags from each other for subsequent stacking and shipment.

In the hands of the user, the bags may be conveniently filled in vertical position through their open mouths, whereupon the mouths of the bags may be resealed in conventional fashion, including the heat sealing together of the uppermost end of the tubular liner. To this end, the upper ends of the bags may be juxtaposed and passed between a pair of horizontally disposed sealing bars similar to those already described. It will be understood of course, that the taping, stitching and heat sealing operation just described may be concurrently performed on the opposite end of the bag lengths by means of a duplicate set of components mounted along the opposite side of the machine frame 13. In such event, provision will be made for a filling aperture, such as a valve and sleeve, which may be subsequently sealed. For example, the valved bags could be provided with an outwardly projecting sleeve formed from polyethylene or similar heat scalable material which, subsequent to filling, could be sealed and the projecting end tucked into the valve.

Modifications may, of course, be made in the invention without departing from its spirit and purpose. For example, while in the instant embodiment of the invention, the heat sealing of the tubular liner is effected subsequent to the taping and stitching of the bag ends, the heat sealing unit could be mounted on the machine frame ahead of the taping and stitching stations and a single, relatively wide heat seal effected across the ends of the liners, whereupon the line of stitching would pass through the seam area intermediate the opposing side edges thereof. Such an arrangement is illustrated in FIGURE 7 of the drawings wherein it will be seen that the heat sealing unit 22a is positioned in advance of the tape applicator and stitching means. Heat sealing subsequent to taping and stitching is preferred, however, since sealing prior to stitching presents problems of the stitching needles being fouled by the still tacky material from which the liner is formed. It has also been found advantageous to provide the trailing pinch rolls 24 with a means of constant pressure in the form of cylinders 52 which would apply the same pressure on the tape between adjacent bags, as well as the bags themselves, as these bags are pulled through the pinch rolls 24, thus achieving a constant speed of the bags passing through the heat sealer. Other modifications will undoubtedly occur to the skilled Worker in the art upon reading these specifications, and consequently it is not intended that the invention be limited in any way excepting as set forth in the claims which follow.

Having thus described the invention in an exemplary embodiment, what is desired to be secured and protected by Letters Patent is:

l. A method for continuously forming multi-wall bags having an inner liner composed of heat sealable material, such as polyethylene, which comprises advancing a plurality of paper webs and a preformed tube of liner forming material, superposing said paper webs and said liner tube with said liner tube overlying said paper webs and spaced inwardly from the opposite side edges thereof, concurrently infolding the opposite side edges of said paper webs about said liner tube and joining together their corresponding edges to provide a plurality of tubes lying one within the other, with said liner tube innermost, severing said combined tubes crosswise into bag lengths,

and thereafter advancing said bag lengths so formed in a direction at right angles to their length, closing the ends of said bag lengths by heat sealing at least one end of each inner liner through the surrounding paper tubes to form an end seal for said liner tube and closing the corresponding ends of said surrounding paper tubes by a line of stitching extending along marginal end portions of said surrounding tubes and passing completely through all of the plies of said bag length including said inner liner, said line of stitching passing through the sealed end of said liner tube along a line spaced outwardly from the innermost edge of said end seal, whereby said line of stitching secures said inner liner to the surrounding plies of the bag so formed and yet does not interfere with the sealed condition of said inner liner.

2. The method claimed in claim 1 including the step of applying tension to the ends of the bag lengths in the direction of this path of travel at least during the time the inner liners are being sealed.

3. The method claimed in claim 2 wherein said inner liners are heat sealed subsequent to the application of said line of stitching, and wherein the seal so formed comprises inner and outer portions lying on opposite sides of said line of stitching.

4. The method claimed in claim 2 wherein the inner liners are heat sealed prior to the application of the line of stitching, and wherein the end seal so formed is continuous throughout its width.

References Cited in the file of this patent UNITED STATES PATENTS 866,902 Adams Sept. 24, 1907 2,000,928 Cundall et al May 14, 1935 2,020,301 Cundall Nov. 12, 1935 2,428,440 Waters Oct. 7, 1947 2,435,743 Geimer Feb. 10, 1948 2,468,695 Wallace Apr. 26, 1949 2,564,594 Clarke Aug. 14, 1951 2,633,286 Claridge et al. Mar. 31, 1953 2,786,622 Ross Mar. 26, 1957 2,975,955 McCurry Mar. 21, 1961 

1. A METHOD FOR CONTINUOUSLY FORMING MULI-WALL BAGS HAVING AN INNER LINER COMPOSED OF HEAT SEALABLE MATERIAL, SUCH AS POLYTHYLENE, WHICH COMPRISES ADVANCING A PLURALITY OF PAPER WEBS AND A PREFORMED TUBE OF LINER FORMING MATERIAL, SUPERPOSING SAID PAPER WEBS AND SAID LINER TUBE WITH SAID LINER TUBE OVERLYING SAID PAPER WEBS AND SPACED INWARDLY FROM THE OPPOSITE SIDE EDGES THEREOF, CONCURRENTLY INFOLDING THE OPPOSITE SIDE EDGES OF SAID PAPER WEBS ABOUT SAID LINER TUBE AND JOINING TOGETHER THEIR CORRESPONDING EDGES TO PROVIDE A PLURALITY OF TUBES LYING ONE WITHIN THE OTHER, WITH SAID LINER TUBE INNERMOST, SEVERING SAID COMBINED TUBES CROSSWISE INTO BAG LENGTHS, AND THEREAFTER ADVANCING SAID BAG LENGTHS SO FORMED IN A DIRECTION AT RIGHT ANGLES TO THEIR LENGTH, CLOSING THE ENDS OF SAID BAG LENGTHS BY HEAT SEALING AT LEAST ONE END OF EACH INNER LINER THROUGH THE SURROUNDING PAPER TUBES TO FORM AN END SEAL FOR SAID LINER TUBE AND CLOSING THE CORESPONDING ENDS OF SAID SURROUNDING PAPER TUBES BY A LINE OF STITCHING EXTENDING ALONG MARGINAL END PORTIONS OF SAID SURROUNDING TUBES AND PASSING COMPLETELY THROUGH ALL OF THE PLIES OF SAID BAG LENGTH INCLUDING SAID INNER LINER, SAID LINE OF STITCHING PASSING THROUGH THE SEALED END OF SAID LINER TUBE ALONG A LINE SPACED OUTWARDLY FROM THE INNERMOST EDGE OF SAID END SEAL, WHEREBY SAID LINE OF STITCHING SECURES SAID INNER LINER TO THE SURROUNDING PLIES OF THE BAG SO FORMED AND YET DOES NOT INTERFERE WITH THE SEALED CONDITION OF SAID INNER LINER. 